In a wide variety of medical research and treatment techniques, notably those related to immunology and cell diseases, a preliminary requirement is the availability of relatively large quantities of functional cells, either singly or in small aggregates, which cells (parenchyma) have been separated from the stroma, i.e., the skeletal or connective cells which support them in the particular organ but which do not directly perform the function of that organ. The process of treating biological tissue so as to remove the stroma and separate out the parenchyma into individual cells with intact membranes is called disaggregation.
Disaggregation has been carried out by a variety of methods. One of them, homogenization, involves breaking up the tissue in a vessel by high-speed whirling blades. Grinding techniques have been employed wherein the tissue is ground between a pestle and a screen to break up the cells. Neither method provides a satisfactory yield of intact cells.
Perfusion is a technique wherein the natural blood vessel structure is employed to carry to the cells an agent which breaks down the adhering forces between cells and between cells and stroma. However, this changes the cell membranes beyond use.
Certain methods of disaggregation are described in a PhD Thesis of D. L. McCollester, entitled "Studies of the Isolation of Cell Membranes With Particular Reference to Skeletal Muscle", University of Cambridge, November, 1962. As outlined in the thesis, isolation of cell membranes first requires cell diaggregation, described as carried out initially on certain muscle tissue. Since the cell membrane in muscle tissue is about six times as thick as for other tissues, muscle can be disaggregated by homogenization without unduly destroying the membranes. However, the technique destroys too high a proportion of membrane of other parenchyma to permit obtaining useful quantities of cells.
Mortar and pestle-type apparatus has also been employed for cell disaggregation in which cells to be treated are placed on Nylon gauze within the mortar and rubbed and pressed vigorously between the pestle and the gauze (see Vaage, "A Mechanical Technique for Obtaining High Yields of Viable, Dispersed Tumor Cells", Transplantion, Vol. 6, No. 1 (January, 1968, pp. 137-39). However, the mechanical forces applied to the cells by this procedure tend to unduly damage the cell membranes, and the yield of intact cells is insufficient for certain purposes, e.g. those described in the McCollester Thesis, supra.